Radio telephone subscriber unit

ABSTRACT

Disclosed is a radio telephone subscriber unit for communicating with a telephone company base terminal wherein control signals are transmitted between the base terminal and the subscriber unit for establishing a radio link-up therebetween. The subscriber unit can be operated in either an automatic or a manual mode. In the automatic mode, the control signals are transmitted by turning on and turning off discrete audio-frequency tones which are modulated onto radio-frequency carrier signals which are generated and transmitted by radio-frequency transmitters in the subscriber unit and at the base terminal. When the telephone call is originated by the base terminal, the audio-frequency control tones or signalling tones received and detected by the subscriber unit are converted into digital signals which are supplied to digital control logic within the subscriber unit. The control logic determines whether the coding of the tone-derived digital signals represent the phone number of the subscriber unit and, when the determination is affirmative, causes the subscriber unit to transmit certain acknowledgement and connect signals back to the base terminal for completing the radio link-up. When the telephone call is originated by the subscriber unit, the same control logic causes the subscriber unit to transmit coded tone burst signals to the base terminal for establishing a radio linkup therewith and for supplying thereto an indication of the phone number of the telephone being called. The subscriber unit includes an automatic channel search mechanism for enabling the subscriber unit to automatically tune in to an idle one of several base terminal carrier channels. The subscriber unit is particularly adapted for use as a self-contained portable battery operated unit and the subscriber unit includes means for automatically switching a significant portion of the control logic to a power conserving standby condition during the voice conversation portion of a telephone call as well as when a telephone call is not in progress. This minimizes the power drain on the power supply battery. In the manual mode, the control logic functions in a somewhat simpler manner, such control logic then being used only on base terminal originated calls to decode coded tone burst signals and to activate a ringing circuit in the subscriber unit when the proper phone number is received. In both modes, various provisions are made for minimizing the power drain on the power supply battery.

United States Patent Peek et al.

RADIO TELEPHONE SUBSCRIBER UNIT Inventors: Benjamin Roger Peek, Garland,

Tex.; Hernando Javier Garcia, San Francisco, Calif.

Vogelman et al 179/41 A Primary Examiner-William C. Cooper Assistant Examiner-Thomas L. Kundrt Attorney, Agent, or Firm-Jack A. Kanz [5 7 ABSTRACT Disclosed is a radio telephone subscriber unit for communicating with a telephone company base terminal wherein control signals are transmitted between the base terminal and the subscriber unit for establishing a radio link-up therebetween. The subscriber unit can be operated in either an automatic or a manual mode. In the automatic mode, the control signals are transmitted by turning on and turning off discrete audiofrequency tones which are modulated onto radiofrequency carrier signals which are generated and Apr. 23, 1974 transmitted by radio-frequency transmitters in the subscriber unit and at the base terminal. When the telephone call is originated by the base terminal, the audio-frequency control tones or signalling tones received and detected by the subscriber unit are converted into digital signals which are supplied to digital control logic within the subscriber unit. The control logic determines whether the coding of the tonederived digital signals represent the phone number of the subscriber unit and, when the determination is affirmative, causes the subscriber unit to transmit certain acknowledgement and connect signals back to the base terminal for completing the radio link-up. When the telephone call is originated by the subscriber unit, the same control logic causes the subscriber unit to transmit coded tone burst signals to the base terminal for establishing a radio link-up therewith and for supplying thereto an indication of the phone number of the telephone being called. The subscriber unit includes an automatic channel search mechanism for enabling the subscriber unit to automatically tune in to an idle one of several base terminal carrier channels. The subscriber unit is particularly adapted for use as a self-contained portable battery operated unit and the subscriber unit includes means for automatically switching a significant portion of the control logic to a power conserving standby condition during the voice conversation portion of a telephone call as well as when a telephone call is not in progress. This minimizes the power drain on the power supply battery. In the manual mode, the control logic functions in a somewhat simpler manner, such control logic then being used only on base terminal originated calls to decode coded tone burst signals and to activate a ringing circuit in the subscriber unit when the proper phone number is received. In both modes, various provisions are made for minimizing the power drain on the power supply battery.

42 Claims,-2l Drawing Figures RING GATE ["0 r. M. AUDIO RECEIVER n4 4* f I58 TONE MUTING LOCAL DETECTOR CIRCUIT osc SIGNAL lL- JSL DIAL EARPHONE H60K T SEARCH .38;? DIAL TELEPHONE (HG 5) HANDSET 1 use W T '26 J- TALK SWITCH g I02 I06 CHANNEL MIKE HOLD 7 ex DY CX TONE I34 GENERATOR TONE F M. I TRANSMITTER ON OFF VOlCE J;- ,(BO POWER OUT" DEMAND 3 POWER 42/ SUPPLY +A0- BATTERy BATT XM|T +Bo- OPERATED I62 POWER IN Q 5%,?

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1. A radio telephone subscriber unit for transmitting radio signals to and receiving radio signals from a radio telephone base terminal, said subscriber unit including control logic circuit means for generating control signals for controlling the operation of the subscriber unit, said control logic circuit means including circuitry for processing signals received from said base terminal, battery operated power supply means for providing operating power for the subscriber unit, and power supply control means coupled between the battery operated power supply means and said processing circuitry of the control logic circuit means and responsive to a first signal generated by the control logic circuit means for allowing the flow of operating power to said processing circuitry to thereby enable said circuitry to process subsequently received signals and responsive to a second signal generated by the control logic circuit means for disabling the flow of operating power to said processing circuitry.
 2. A radio telephone subscriber unit for transmitting radio signals to and receiving radio signals from a radio telephone base terminal, said subscriber unit including control logic circuit means including circuitry for generating a first signal when establishment of a radio link-up between the subscriber unit and the radio telephone base terminal is initiated and circuitry for generating a second signal when such radio link-up is established and following transmission by the subscriber unit of a certain signal to the base terminal, battery operated power supply means for providing operating power for the subscriber unit, and power supply control means coupled between the battery operated power supply means and predetermined circuitry of the control logic circuit means and responsive to said first signal for enabling the flow of operating power to the predetermined circuitry and responsive to said second signal for disabling the flow of operating power to the predetermined circuitry.
 3. A radio telephone subscriber unit for transmitting radio signals to and receiving radio signals from a radio telephone base terminal, said subscriber unit including control logic circuit means including circuitry for generating a first signal when disconnection of a radio link-up between the subscriber unit and the radio telephone base terminal is initiated and circuitry for generating a second signal upon completion of disconnection of the radio link-up, battery operated power supply means for providing operating power for the subscriber unit, and power supply control means coupled between the battery operated power supply means and predetermined circuitry of the control logic circuit means and responsive to said first signal for enabling the flow of operating power to the predetermined circuitry and responsive to said second signal for disabling the flow of operating power to the predetermined circuitry.
 4. A radio telephone subscriber unit for transmitting radio signals to and receiving radio signals from a radio telephone base terminal, said subscriber unit including control logic circuit meanS for generating control signals for controlling the operation of the subscriber unit, battery operated power supply means for providing operating power for the subscriber unit, and power supply control means coupled between the battery operated power supply means and predetermined circuitry of the control logic circuit means and responsive to a first signal generated by the control logic circuit means for enabling the flow of operating power to the predetermined circuitry and responsive to a second signal generated by the control logic circuit means for disabling the flow of operating power to the predetermined circuitry. said power supply control means including a power input terminal connected to said battery operated power supply means, a power output terminal connected to said predetermined circuitry, bistable means responsive to said first signal for generating an enabling signal and responsive to said second signal for generating a disabling signal, and means interconnecting said input terminal and said output terminal and responsive to said enabling signal for allowing the transfer of operating power from said input terminal to said output terminal and responsive to said disabling signal for preventing the transfer of operating power from said input terminal to said output terminal.
 5. A radio telephone subscriber unit as in claim 4 wherein said interconnecting means includes a first transistor whose emitter and collector are connected in series between said power input terminal and said power output terminal, and a second transistor coupled to said bistable means and to said first transistor, said second transistor operative to conduct current in response to said enabling signal and to inhibit the conduction of current in response to said disabling signal, and said first transistor operative to allow the transfer of operating power therethrough when said second transistor is conducting and to prevent the transfer of operating power therethrough when said second transistor is not conducting.
 6. A radio telephone subscriber unit for transmitting radio signals to and receiving radio signals from a radio telephone base terminal, said subscriber unit including control logic circuit means for generating control signals for controlling the operation of the subscriber unit, battery operated power supply means for providing operating power for the subscriber unit, and power supply control means coupled between battery operated power supply means and predetermined circuitry of the control logic circuit means and responsive to a first signal generated by the control logic circuit means for enabling the flow of operating power to the predetermined circuitry and responsive to a second signal generated by the control logic circuit means for disabling the flow of operating power to the predetermined circuitry, said power supply control means further including circuitry for generating an inhibit signal in response to said second signal, and said control logic circuit means including circuitry responsive to said inhibit signal for preventing the transmission of radio signals to the base terminal.
 7. A radio telephone subscriber unit for use in a two-way radio telephone system in which a radio telephone base terminal transmits an idle tone signal to identify an available radio channel and a seize tone signal to initiate a telephone call between the base terminal and a selected subscriber unit, said radio telephone subscriber comprising control logic circuit means for generating control signals to control the operation of said subscriber unit and including circuitry for generating a first signal in response to the transmission of a seize tone signal by the base terminal, battery operated power supply means for supplying operating power for said subscriber unit, and power supply control means coupled between said battery operated power supply means and predetermined portions of said control logic circuit Means and responsive to said first signal for allowing the flow of operating power to said predetermined portions and responsive to certain other control signals from said control logic circuit means for preventing the flow of operating power to said predetermined portions.
 8. A radio telephone subscriber unit for use in a two-way telephone system in which a radio telephone base terminal transmits an idle tone signal to identify an available radio channel, a seize tone signal to initiate a telephone call between the base terminal and a selected subscriber unit, and a called number signal sequence to identify the selected subscriber unit, said radio telephone subscriber unit comprising control logic circuit means for generating control signals to control the operation of said subscriber unit and including circuitry for generating a second signal if any but a particular called number signal sequence is transmitted by said base terminal, battery operated power supply means for supplying operating power for said subscriber unit, and power supply control means coupled between said battery operated power supply means and predetermined portions of said control logic circuit means and responsive to certain of said control signals for allowing the flow of operating power to said predetermined portions and responsive to said second signal for preventing the flow of operating power to said predetermined portions.
 9. A radio telephone subscriber unit for use in a two-way telephone system in which a radio telephone base terminal transmits an idle tone signal to identify an available radio channel, a seize tone signal to initiate a telephone call between the base terminal and a selected subscriber unit, and a called number signal sequence to identify the selected subscriber unit, said radio telephone subscriber unit comprising control logic circuit means for generating control signals to control the operation of said subscriber unit and including circuitry for generating a second signal if more than a certain predetermined period of time elapses between transmission of various portions of the called number signal sequence by the base terminal, battery operated power supply means for supplying operating power for said subscriber unit, and power supply control means coupled between said battery operated power supply means and predetermined portions of said control logic circuit means and responsive to certain of said control signals for allowing the flow of operating power to said predetermined portions and responsive to said second signal for preventing the flow of operating power to said predetermined portion.
 10. A radio telephone subscriber unit for use in a two-way radio telephone system in which a radio telephone base terminal transmits a called number signal sequence to identify a selected subscriber unit, and a ringing signal sequence to notify the selected subscriber unit that that unit is being called, said radio telephone subscriber unit comprising a hook switch having on-hook and off-hook conditions, control logic circuit means for generating control signals to control the operation of said subscriber unit and including circuitry for generating first and second enabling signals if a particular called number signal sequence is transmitted by said base terminal and circuitry responsive to said first enabling signal for generating a third signal a predetermined period of time after termination of transmission of a ringing signal sequence if said hook switch is in the on-hook condition, battery operated power supply means for supplying operating power for said subscriber unit, and power supply control means coupled between said battery operated power supply means and predetermined portions of said control logic circuit means and responsive to certain of said control signals for allowing the flow of operating power to said predetermined portions and responsive to said third signal for preventing the flow of operating power to said predetermined portions.
 11. A radio telephone subscriber unit as in claim 10 wherein said control logic circuit means further includes circuitry responsive to said second enabling signal for generating a fourth signal if said hook switch is placed in the off-hook condition and wherein said power supply control means further includes circuitry responsive to said fourth signal for preventing the flow of operating power to said predetermined portions.
 12. A radio telephone subscriber unit as in claim 11 wherein said control logic circuit means further includes circuitry responsive to said fourth signal for generating a third enabling signal and circuitry responsive to said third enabling signal for generating said first signal upon said hook switch being placed in the on-hook condition.
 13. A radio telephone subscriber unit as in claim 12 wherein said control logic circuit means further includes circuitry responsive to the generation of said first signal in response to said third enabling signal for generating a disconnect signal sequence of predetermined duration and circuitry for generating a fifth signal upon termination of generation of said disconnect signal sequence and wherein said power supply control means further includes circuitry responsive to said fifth signal for preventing the flow of operating power to said predetermined portions.
 14. A radio telephone subscriber unit for use in a two-way radio telephone system in which a radio telephone base terminal transmits an idle tone signal to identify an available radio channel, a seize tone signal to initiate a telephone call between the base terminal and a selected subscriber unit, a called number signal sequence to identify the selected subscriber unit, and a ringing signal sequence to notify the selected subscriber unit that that unit is being called, said radio telephone subscriber unit comprising a hook switch having on-hook and off-hook conditions, control logic circuit means for generating a first signal in response to the hook switch being placed in the off-hook condition, battery operated power supply means for supplying operating power for said subscriber unit, and power supply control means coupled between said battery operated power supply means and predetermined portions of said control logic circuit means and responsive to said first signal for allowing the flow of operating power to said predetermined portions.
 15. A radio telephone subscriber unit as in claim 14 wherein said control logic circuit means further includes circuitry for generating a second signal if, after a first predetermined period of time, the idle tone signal is not being transmitted by the base terminal or if, after a second predetermined period of time, the idle tone signal is being transmitted by the base terminal, and wherein said power supply control means further includes circuitry responsive to said second signal for preventing the flow of operating power to said predetermined portions.
 16. A radio telephone subscriber unit as in claim 15 wherein said control logic circuit means further includes circuitry for generating the second signal if, within a third predetermined period of time, the seize tone signal is not being transmitted by the base terminal.
 17. A radio telephone subscriber unit as in claim 14 wherein said subscriber unit further includes means for producing dialed signal sequences for transmission to the base terminal, each such dialed signal sequence representing a digit of a called telephone number, wherein said control logic circuit means further includes circuitry for producing an identification signal sequence for transmission to the base terminal, said identification signal sequence for identifying said subscriber unit, circuitry for generating and enabling signal after production of the identification signal sequence, and circuitry responsive to said enabling signal when the hook switch is in the off-hook condition for generating a third signal if no dialed Signal sequence is produced within a predetermined period of time after generation of said enabling signal or if no dialed signal sequence is produced within a predetermined period of time after the production of each dialed signal sequence, and wherein said power supply control means includes circuitry responsive to said third signal for preventing the flow of operating power to said predetermined portions.
 18. A radio telephone subscriber unit as in claim 17 wherein said control logic circuit means further includes circuitry responsive to said enabling signal for generating said first signal when said hook switch is placed in the on-hook condition.
 19. A radio telephone subscriber unit as in claim 18 wherein said control logic circuit means further includes circuitry responsive to the generation of said first signal when said hook switch is placed in the on-hook condition for generating a disconnect signal sequence of predetermined duration and circuitry for generating a fourth signal upon termination of generation of said disconnect signal sequence and wherein said power supply control means further includes circuitry responsive to said fourth signal for preventing the flow of operating power to said predetermined portions.
 20. In a radio telephone system including a radio telephone base terminal for transmitting called number signal sequences and ringing signal sequences and at least one radio telephone subscriber unit, said subscriber unit including control logic means for producing control signals for controlling the operation of the subscriber unit, battery operated power supply means for supplying operating power to the subscriber unit, power supply control means interconnecting the battery operated power supply means with certain circuitry of the control logic means, microphone and earphone circuitry, and a hook switch for enabling transmission of voice signals to and reception of voice signals from the base terminal by means of the microphone and earphone circuitry respectively when the hook switch is in a first position and for disabling transmission of voice signals to and reception of voice signals from the base terminal when the hook switch is in a second position, a method of controlling the flow of operating power to said certain circuitry comprising the steps of a. enabling the flow of operating power to said certain circuitry when the base terminal transmits a seize tone signal, b. disabling the flow of operating power to said certain circuitry when any but a particular called number signal sequence is transmitted by the base terminal, c. disabling the flow of operating power to said certain circuitry upon termination of transmission of a ringing signal sequence by the base terminal if, upon such termination, the hook switch is in the second position, d. disabling the flow of operating power to said certain circuitry a predetermined period of time after the hook switch is placed in the first position following transmission of a ringing signal sequence, e. enabling the flow of operating power to said certain circuitry upon replacing the hook switch in the second position, and f. disabling the flow of operating power to said certain circuitry a predetermined period of time after the replacement of the hook switch in the second positionn.
 21. In a radio telephone system including a radio telephone base terminal for transmitting called number signal sequences and ringing signal sequences and at least one radio telephone subscriber unit, said subscriber unit including control logic means for producing control signals for controlling the operation of the subscriber unit, battery operated power supply means for supplying operating power to the subscriber unit, power supply control means interconnecting the battery operated power supply means with certain circuitry of the control logic means, means for producing dialed signal sequences for transmission to the base terminal, means for producing an identification sIgnal sequence, microphone and earphone circuitry, and a hook switch for enabling transmission of voice signals to and reception of voice signals from the base terminal by means of the microphone and earphone circuitry respectively when the hook switch is in a first position and for disabling transmission of voice signals to and reception of voice signals from the base terminal when the hook switch is in a second position, a method of controlling the flow of operating power to said certain circuitry comprising the steps of a. enabling the flow of operating power to said certain circuitry when the hook switch is placed in the first position, b. disabling the flow of operating power to said certain circuitry if, after a first predetermined period of time, an idle tone signal is not being transmitted by the base terminal or if, after a second predetermined period of time, an idle tone signal is being transmitted by the base terminal, c. disabling the flow of operating power to said certain circuitry if, within a third predetermined period of time, a seize tone signal is not being transmitted by the base terminal, d. disabling the flow of operating power to said certain circuitry when no dialed signal sequence is produced within a predetermined period of time following production of the identification signal sequence or when no dialed signal sequence is produced within a predetermined period of time following production of a previous dialed signal sequence, e. enabling the flow of operating power to said certain circuitry upon replacing the hook switch in the second position, and f. disabling the flow of operating power to said certain circuitry a predetermined period of time after the replacement of the hook switch in the second position.
 22. A radio telephone subscriber unit for use in a radio telephone system in which a radio telephone base terminal identifies a selected subscriber unit by transmitting a called number signal sequence representing that subscriber unit''s identification number and then notifies the selected subscriber unit by transmitting an audio ringing signal sequence, said subscriber unit comprising a receiver for receiving signals transmitted by the base terminal, a speaker for generating audible signals, an amplifier responsive to audio signals applied thereto for actuating said speaker in accordance with the audio signals control logic means responsive to the receipt by the subscriber unit of a particular called number signal sequence for generating a control signal, and means coupled between said receiver and said amplifier and responsive to said control signal for applying to said amplifier ringing signal sequences received by said receiver.
 23. A radio telephone subscriber unit as in claim 22 wherein said control logic means further includes circuitry responsive to the receipt by the subscriber unit of said particular called number signal sequence for causing said amplifier to increase its gain by a predetermined amount.
 24. A radio telephone subscriber unit for use in a radio telephone system in which a radio communication channel may be established and maintained between the subscriber unit and a radio telephone base terminal so long as a radio signal is transmitted between the base terminal and subscriber unit within a predetermined interval of time following establishment of the channel or following any transmission of a radio signal, said subscriber unit comprising a transmitter for transmitting radio signals over the radio communication channel, and control logic means for monitoring said transmitter to determine when radio signals are being transmitted and for actuating said transmitter to transmit a radio signal burst if no signals were transmitted by the transmitter in a preceding predetermined time interval.
 25. The radio telephone subscriber unit as in claim 24 further including means for generating modulating signals, and wherein said transmitter incluDes means for generating radio signals, means for applying the radio signals to the radio communication channel, gating means coupled between said radio signal generating means and said applying means and responsive to the presence of an enabling signal for allowing passage of signals from said radio signal generating means to said applying means, and activating means responsive to the presence of an activating signal from said control logic means and to the presence of said modulating signals for producing an enabling signal of duration substantially equal to the duration of the activating signal or modulating signal present.
 26. The radio telephone subscriber unit as in claim 25 wherein said control logic means includes means coupled to said activating means for generating a first signal whenever said enabling signal is being produced and for generating a second signal whenever said enabling signal is not being produced, and timing means responsive to the generation of said second signal for producing an activating signal of certain duration after a predetermined time interval unless said first signal is generated within that time interval.
 27. The radio telephone subscriber unit as in claim 26 wherein said timing means includes a capacitor, means responsive to said second signal for enabling said capacitor to charge and responsive to said first signal for discharging said capacitor, and trigger circuit means for producing said activating signal and discharging said capacitor when the voltage across said capacitor reaches a predetermined level.
 28. A radio telephone subscriber unit as in claim 24 wherein said control logic means includes means for producing a first signal when a particular signal sequence is transmitted by the base terminal, means for producing a second signal following transmittal of said particular signal sequence by the subscriber unit, and means responsive to said first and second signals for activating said transmitter to transmit said signal burst if no signals are transmitted by the transmitter within a particular time interval.
 29. A radio telephone subscriber unit as in claim 28 wherein said transmitter includes means for generating radio signals, means for applying the radio signals to a radio communication channel, activating means including an output line and responsive to an activating signal from said control logic means for applying a gating signal of predetermined duration to said output line, gating means coupled between radio signal generating means and said applying means and responsive to the presence of said gating signal on said output line for enabling signals from said radio signal generating means to be applied to said applying means, and wherein said control logic means includes means for generating control signals for establishing a radio communication channel between the subscriber unit and the base terminal and means responsive to various ones of said control signals for applying gating signals to said output line.
 30. A radio telephone subscriber unit for use in a radio telephone system which includes a radio telephone base terminal which transmits a plurality of radio signals for establishing a radio link-up with the subscriber unit, said subscriber unit including means for receiving the radio signals transmitted by the base terminal and for generating digital signals representing such radio signals, said digital signals including combinations of idle tone signal bursts and seize tone signal bursts, each combination representing a digit of a subscriber unit identification number, and a control logic unit for producing a plurality of control signals to control the operation of the subscriber unit, said control logic unit including timing means for producing a plurality of timing signals at predetermined timing intervals following activation of the timing means, and timing control means responsive to certain ones of said digital siGnals and said control signals for resetting and activating said timing means at certain times during the course of establishing the radio link-up, responsive to certain other of said digital signals in said control signals for resetting and deactivating said timing means at certain other times during the course of establishing the radio link-up, and responsive to each idle tone signal burst and each seize tone signal burst of a combination for resetting and activating said timing means.
 31. A radio telephone subscriber unit as in claim 30 wherein said control logic unit further includes means for producing a first signal when a particular combination of idle and seize tone signal bursts is generated, and wherein said timing control means further includes circuitry responsive to said first signal for resetting and deactivating said timing means.
 32. A radio telephone subscriber unit as in claim 30 wherein said control logic unit further includes means for producing a second signal after a particular combination of idle and seize tone signal bursts has been generated, and wherein said timing control means further includes circuitry responsive to said second signal for resetting and activating said timing means.
 33. A radio telephone subscriber unit as in claim 30 further including a hook switch having on-hook and off-hook conditions, and wherein said control logic unit further includes means for producing a third signal when said hook switch is placed in the off-hook condition following generation of a particular combination of idle and seize tone signal bursts, and wherein said timing control means further includes circuitry responsive to said third signal for resetting and activating said timing means.
 34. A radio telephone subscriber unit as in claim 33 wherein said control logic unit further includes means for producing a fourth signal when said hook switch is replaced in the on-hook condition, and wherein said timing control means further includes circuitry responsive to said fourth signal for resetting and activating said timing means.
 35. A radio telephone subscriber unit which includes a radio telephone base terminal which transmits a plurality of radio signals for establishing a radio link-up with the subscriber unit, said subscriber unit including means for receiving the radio signals transmitted by the base terminal and for generating digital signals representing such radio signals, a hook switch having on-hook and off-hook conditions, a logic unit for producing a first signal when said hook switch is placed in the off-hook condition, timing means for producing a plurality of timing signals at predetermined timing intervals following activation of the timing means, and timing control means responsive to said first signal for resetting and activating said timing means, responsive to a particular timing signal produced by said timing means following production of said first signal for resetting and deactivating said timing means, and responsive to a particular digital signal for thereafter activating said timing means.
 36. A radio telephone subscriber unit as in claim 35 wherein said control logic unit further includes means for producing a second signal when said hook switch is replaced in the on-hook condition and wherein said timing control means further includes circuitry responsive to said second signal for resetting and activating said timing means.
 37. A radio telephone subscriber unit for use in a radio telephone system having a radio telephone base terminal which transmits a called number signal sequence specifying a subscriber unit identification number, said subscriber unit comprising: means for receiving said signal sequence, means for producing a first plurality of digital counts, each of said counts representing the value of a different one of the digits of the identification number specified by said signal sequence, means for successively storing each of said counts, means for producing a second plurality of digital counts, each representing the value of a different one of the digits of an identification number assigned to said subscriber unit, means for comparing each count stored in said storing means with a corresponding count produced by said second plurality producing means, means responsive to said comparing means for producing a parity signal each time a pair of compared counts match, means for clearing said storing means each time a parity signal is produced in preparation for storing the succeeding count, means for causing said second plurality producing means to produce the succeeding count of the second plurality each time a parity signal is produced, means for producing a no-parity signal each time a pair of compared counts fails to match, means for generating a last-digit signal if all pairs of compared counts match, timing means for producing a time-out signal a predetermined period of time after each parity signal is produced unless a succeeding digital count is stored in said storing means within said predetermined period or unless a last-digit signal is generated, and means responsive to said no-parity signal or said time-out signal for deactivating a predetermined portion of the subscriber unit components.
 38. A radio telephone subscriber unit as in claim 37 wherein said storing means comprises a binary counter and said second plurality producing means includes circuitry for producing binary counts.
 39. A radio telephone subscriber unit as in claim 37 further including means for successively generating a pulse signal, means responsive to said pulse signals for transmitting to the base terminal radio signals representing said pulse signals, means for applying each pulse signal to said storing means to thereby cause said storing means to increase its count by one, means responsive to said parity signal for temporarily inhibiting the generation of pulse signals to allow for clearing said storing means and to allow said second plurality of producing means to produce a succeeding count of the second plurality of counts, the resulting radio signals transmitted to the base terminal thereby representing the identification number assigned to the subscriber unit.
 40. A radio telephone subscriber unit as in claim 39 further including means for inhibiting further generation of pulse signals after a predetermined number of counts has been produced by said second plurality of producing means.
 41. A radio telephone subscriber unit for use in a radio telephone system having a radio telephone base terminal which transmits a called number signal sequence specifying a subscriber unit identification number, said subscriber unit comprising: means for receiving said signal sequence, means for producing a first plurality of digital counts, each of said counts representing the value of a different one of the digits of the identification number specified by said signal sequence, means for successively storing each of said counts, means for producing a second plurality of digital counts, each representing the value of a different one of the digits of an identification number assigned to said subscriber unit, means for comparing each count stored in said storing means with a corresponding count produced by said second plurality producing means, means responsive to said comparing means for producing a parity signal each time a pair of compared counts match, means for clearing said storing means each time a parity signal is produced in preparation for storing the succeeding count, means for causing said second plurality producing means to produce the succeeding count of the second plurality each time a parity signal is produced, and wherein said second plurality producing means comprises decoder means having a plurality of output lines, each representing a different digit of the identification number assigned to the subscriber unit, aNd responsive to said parity signals for successively energizing each of said output lines, decimal-to-binary converter means having a plurality of input lines, each representing a different of the decimal digits, and responsive to the energization of an input line for producing a binary count equivalent to the value of the decimal digit represented by that input line, and, means for connecting said output lines to various ones of said input lines so that as the output lines are successively energized the converter means is caused to produce a plurality of counts representing the identification number assigned to the subscriber unit.
 42. A radio telephone subscriber unit as in claim 41 further including a mode switch having a manual position and an automatic position and means for generating a first signal when said mode switch is in the manual position and for generating a second signal when the mode switch is in the automatic position, and wherein said decoder means includes means responsive to said first signal for energizing a different one of a first set of said output lines in response to said parity signal and means responsive to said second signal for energizing a different one of a second set of said output lines in response to said parity signal. 